1. Field of the Invention
The present invention relates to a camera provided with a lens barrier apparatus. In particular, the present invention is directed to a lens barrier apparatus which is provided as a barrier to cover the lens when the camera is not in use.
2. Description of the Related Art
A camera may include a lens barrier apparatus that operates such that when the camera is turned ON, a lens barrel containing the lens (or lens group) moves from a housed position in which the lens barrier is closed, to a photo-ready position in which the lens barrier is open. Similarly, when the camera is turned OFF, the lens barrel moves from the photo-ready position in which the barrier apparatus is open, to a housed position in which the barrier apparatus is closed.
In most cases, including zoom lens cameras, a lens barrel motor is provided to drive the lens barrel from the housed position to the photo-ready position. Thus, a conventional method of driving the barrier apparatus is to use the lens barrel motor to open and close the barrier apparatus.
One such method uses a spring-loaded barrier apparatus that is designed such that the barrier is constantly urged in the opening direction by a spring. In this case, as the lens barrel moves from the housed position to the photo-ready position, a catch is released such that a stored spring force is released to open the barrier. Then, when the lens barrel motor drives the lens bar barrel from the photo-ready position to the housed position, the barrier is closed against the force of the spring by a cam mechanism or the like and the spring is reset to prepare for the next opening operation.
With such a barrier apparatus, the motor must operate against the force of the spring in order to close the barrier. As such, the motor, and in particular, the contact points between a cam pin and a barrier driving ring are subject to a load. In this case, misalignment of the cam pin and the barrier driving ring could result in a failure. Further, in the particular case of a zoom lens, in which the lens barrel motor may be used to drive a number of lens barrels, the additional load may require a larger lens barrel motor.
Since in the above method the opening of the barrier is spring-biased, if the barrel has accidentally been exposed to a sticky liquid, such as juice or the like, the barrier may not open correctly because the spring force cannot overcome the external sticking force. In this case, a larger than usual force is required at the initial stages of the opening operation. However, if a stronger spring is used in order to provide a larger force to overcome the external force, the design choices available become more restricted and there is a higher probability of failure because of wear.
The above problem can be overcome if the barrier apparatus includes a barrier motor that drives the barrier apparatus independently. However, this method also has problems in that, for example, the size of the camera is increased due to the inclusion of an independent barrier motor and the components required for the operation of the barrier motor. Further, with this arrangement, a sensor that determines the condition of the barrier apparatus is required in order to prevent problems if the barrier motor fails. For example, if the barrier motor fails but the lens barrel motor does not, the user may not be aware of the problem and may attempt to take a photograph with the barrier closed, or, store the camera with the barrier open and damage the lens.